Physical exercise is important to the human body. In addition to increasing strength and stamina, physical exercise can increase longevity. Physical exercise commonly makes humans feel good physically and mentally.
Exercise machines have been developed to enable physical exercising to be done in a time-efficient manner. Some exercise machines target largely only a single feature of the human anatomy such as the legs.
Other exercise machines are designed to enable multiple features of the human anatomy, e.g., the legs and arms/shoulders, to be exercised. FIG. 1 illustrates such a multi-function exercise machine as disclosed in U.S. Pat. No. 6,902,515 B2. The prior art exercise machine of FIG. 1 consists of base assembly 20, pedal-revolving pedaling mechanism 22, seat 24, seatback 26, upper-body assembly 28, and rotational arm-shoulder device 30. Pedaling mechanism 22 includes a pair of pedals 32. When actuated by the feet of a person, pedals 32 revolve about an axis to exercise the person's legs. Arm-shoulder device 30 includes a pair of off-center handles 34 which can similarly be revolved about an axis by the person's hands to exercise the person's arms and shoulders.
FIGS. 2a and 2b illustrate two way in which upper-body assembly 28 can be connected to the back of seatback 26 (not shown in FIG. 2a or 2b) to enable portion 36 of assembly 28 to be moved in various ways while a person is exercising with the machine of FIG. 1. In the embodiment of FIG. 2a, back member 38 of movable portion 36 is connected by pin 40 to seatback 26 for enabling portion 36 to pivot from side to side about axis 42 that extends generally parallel to the length of base assembly 20. A pair of springs 44 connected between back member 38 and fixed base member 46 of upper-body assembly 28 provide resistance for the side-to-side movement.
In the embodiment of FIG. 2b, back member 38 is connected by bearing mechanism 48 to fixed base member 50 of upper-body assembly 28 for enabling movable portion 36 to pivot in various manners about bearing mechanism 48 in order to exercise the arms and shoulders. For example, movable portion 36 can pivot from front to back and vice versa about axis 52 that extends generally perpendicular to the length and height of the exercise machine. Movable portion 36 in FIG. 2b can also pivot about axis 54 that extends generally parallel to back member 38. Coil torsion spring 56 provides resistance to the movement of portion 36 in FIG. 2b. Although seat 24 and seatback 26 can be adjusted horizontally along the length of base assembly 20 to accommodate persons of different size, seat 24 and seatback 26 are substantially stationary during exercising usage when upper-body assembly 28 is implemented as shown in both FIG. 2a and FIG. 2b. 
The abdominal muscles of the human body often need strengthening. While the multi-function exercise machine of FIG. 1 appears capable of providing the legs and arms/shoulders with good exercise, the machine of FIG. 1 is not particularly targeted toward the abdominal muscles. It would be desirable to have an exercise machine that can exercise both the legs and abdominal muscles.